增强GNSS受限环境下的5G NTN VSAT随机接入
Enhancing 5G NTN VSAT RACH in GNSS-Denied environments
- European Commission, Joint Research Centre（欧盟委员会联合研究中心）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
针对GNSS受限环境下5G NTN VSAT随机接入依赖GNSS定位的脆弱性，提出基于AoA、FoA和ToA混合的单卫星定位框架，将初始定位不确定性从数十公里降至几公里，实现稳健初始接入。
AI中文摘要：
3GPP 5G非地面网络（NTN）技术从根本上依赖于用户设备（UE）处的全球导航卫星系统（GNSS）定位，以在任何传输（包括用于初始接入的随机接入过程）之前预先补偿用户链路延迟和多普勒频移。在GNSS受限或受干扰的环境中，这种依赖性会导致前导码冲突和连接中断，从而削弱基于卫星的全球连接。为解决这一脆弱性问题，本文提出了一种新颖的单卫星定位框架，专为配备相控阵天线的高频段（Ku或Ka波段）5G NTN甚小口径终端（VSAT）设计。该多步骤方案从到达角（AoA）观测量中推导出初始粗略位置，从低地球轨道（LEO）下行链路参考信号中提取到达频率（FoA）和到达时间（ToA）测量值，并在Levenberg-Marquardt导航滤波器中将其混合。在静态网格和真实动态城市轨迹上的系统评估详细说明了从单历元AoA误差最小化过渡到多历元角度跟踪，随后集成多普勒和测距观测量的增量收益。基于现实的误差预算，所提出的框架将初始定位不确定性从数十公里降低到几公里。这一定位精度水平，结合3GPP Release 20 NR NTN规范中引入的GNSS弹性特性，使得在受损操作环境中能够以对3GPP标准的最小放宽实现稳健的初始接入。
英文摘要：
The 3GPP 5G non-terrestrial networks (NTN) technology fundamentally relies on a global navigation satellite system (GNSS) fix at the user equipment (UE) to pre-compensate for user-link delay and Doppler shifts prior to any transmission, including the random-access procedure for initial access. In GNSS-denied or interfered environments, this dependency triggers preamble collisions and connection dropouts, undermining satellite-based global connectivity. To address this vulnerability, this paper introduces a novel single-satellite positioning framework designed for higher-frequency (Ku- or Ka-band) 5G NTN very small aperture terminals (VSATs) equipped with a phased-array antenna. The multi-step scheme derives an initial coarse position from angle of arrival (AoA) observables, extracts frequency of arrival (FoA) and time of arrival (ToA) measurements from low Earth orbit (LEO) downlink reference signals, and hybridizes them within a Levenberg-Marquardt navigation filter. Systematic evaluations across static grids and realistic dynamic urban trajectories detail the incremental gains of transitioning from single-epoch AoA error minimization to multi-epoch angular tracking, followed by the integration of Doppler and ranging observables. Grounded in a realistic error budget, the proposed framework reduces initial positioning uncertainty from tens of kilometres down to a few kilometres. This level of positioning accuracy, combined with the GNSS-resilient features introduced in 3GPP Release 20 NR NTN specifications, enables robust initial access in compromised operational environments with minimal relaxation of 3GPP standards.
